The characteristics of optical wave transmitted in optical fiber will change under the influence of external factors such as pressure, temperature, vibration, etc. by measuring the change of optical wave parameters, the change of external physical quantities can be perceived. When the external vibration acts on the optical cable, the fiber core will deform, the refractive index and length of the fiber core will change, and the phase of the optical cable will change. When the light is transmitted in the optical cable, the Rayleigh scattering light is continuously transmitted backward due to the interaction between photons and the core lattice. When the external vibration exists, the phase change of backscattered Rayleigh light is converted into the change of light intensity. After photoelectric conversion and signal processing, the data are analyzed by computer. According to the results of the analysis, the system judges the occurrence of the intrusion event and confirms the intrusion location. Therefore, the characteristics of optical fiber sensitive to external factors can be used to timely alarm and locate the hazards in a certain range along the optical fiber, so as to realize real-time protection of important areas or surrounding areas, and reduce unnecessary waste of resources and loss of life and property. Optical fiber early warning system has the advantages of high sensitivity, strong anti electromagnetic interference ability and wide measurement range. It can give an alarm when the threat event has just occurred and has not caused substantial damage to the protected object, so as to contain the threat in the bud. Due to the above advantages, optical fiber early warning technology has been widely used in the safety and health monitoring of large infrastructure, important equipment and energy transmission pipeline, and has become the best choice for many applications.